In the first and the second report of this series, we presented the theory and special characteristic of the jet-apparatus and the utilization of the jet-apparatus for the pressure increaser in the suction pipe. In this 3rd report, we present the problem of the use of the jet-apparatus for the machines used for port and harbor construction.
　Most of the machinery equipments used for the port and harbor construction, and machines in dredgers are used in the water or on the water. So, the utilization of jet-apparatus using the water jet-nozzles are very convienient for use so far as their mechanism and handling are concerned, and despite the inefficiency of the single use of the jet-apparatus itself, it can improve the working effiency of machines as a whole when it is attached to them.
　From the idea above mentioned, we showed here in this report the experimental results gained by the three kind of model machines used as the application of the jet apparatus for the port and harbor construction.
　Following are the main features of model machines.
1) The machine used for the hanging up and shifting concrete-blocks in the water or in the air, utilizing the water jet-apparatus.
2) water and sand transport equipment used for the transport of sand by the hydraulic power from the hopper of the dredgers and hopper burges.
3) Model testing apparatus for the investigation of the relation on the distance between the tip of nozzle and suction mouth, and relation on the shape of suction mouth and pressure capacity regarding jet-apparatus in which the water jet is spread out from the outside of the suction-pipe.
　According to the experimental results gained by these model machines, each machine was proved to be able to display the sufficient efficiency which was planned at the design of each machine.